Sputtered silicon thin films for piezoresistive pressure microsensors

Polycrystalline silicon thin films have been prepared by sputtering techniques, followed by a recrystallization treatment. These films can be used as sensing elements for pressure microsensors that have a semiconductor/ insulator/micromachined-silicon structure. Adjustments of the sensing-element properties, such as resistivity, gauge factor and temperature coefficients, can be made by doping with boron. Gauge factors (GFs) up to 30 and temperature coefficients of resistance (TCR) of 50 ppm/°C are feasible. Boron doping concentrations in the range 1 × 10¹⁸-1 × 10²⁰ cm^-3, corresponding to sheet resistances of 7 × 10⁶-100 Ω/□, have been investigated. Grain sizes and crystallite orientation are also included as microstructural properties.